1. Technical Field
The present invention relates to a liquid ejecting head such as an ink jet-type recording head and a liquid ejecting apparatus provided with such a liquid ejecting head, and particularly relates to a liquid ejecting head and a liquid ejecting apparatus capable of handling high-viscosity liquids.
2. Related Art
A liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting a liquid and that ejects various types of liquid from the liquid ejecting head, causing those liquids to impact upon an impact target. An image recording apparatus such as an ink jet printer (called simply a “printer” hereinafter) that is, for example, provided with an ink jet-type recording head (an example of a liquid ejecting head; called simply a “recording head” hereinafter), and that records images, text, and so on a printing medium such as recording paper, the printing surface of an optical disc, or the like (an example of an impact target) by causing ink in liquid form to be ejected from nozzles in the recording head and impact upon the printing medium, can be given as an example of a typical liquid ejecting apparatus. Meanwhile, in addition to such image recording apparatuses, the ink jet techniques of liquid ejecting apparatuses are recently being applied in various other manufacturing apparatuses as well, such as apparatuses for manufacturing color filters for liquid crystal displays, electrode forming apparatuses, and so on.
The aforementioned liquid ejecting apparatus is sometimes used in applications where the liquid that is ejected has a viscosity of 8 mPa·s or more (called a “high-viscosity liquid” hereinafter). For example, high-viscosity inks are advantageous in that they are less prone to bleeding than low-viscosity inks (that is, inks with a viscosity of less than 8 mPa·s); thus, not only is unevenness in the darkness unlikely to occur in the recorded image, but the ink also dries quickly. Ultraviolet light-curable inks, liquid crystals, and so on that are cured by irradiating the liquid with ultraviolet light are also examples of high-viscosity liquids.
Meanwhile, with such liquid ejecting apparatuses, while it is desirable to eject large ink droplets in order to accelerate so-called solid printing, in which a predetermined region of the recording medium is filled with ink, text printing, in which text characters are printed, and so on, it is also desirable to eject small ink droplets in order to meet the demand for increased resolutions in recorded images and the like. Accordingly, limiting the dimensions of nozzle diameters to a specific range in which small ink droplets can be ejected and furthermore limiting the ejecting amount of the ink droplets to an ejection amount that is within a specific range has been proposed (for example, see JP-A-2004-090223). Attempting to miniaturize ink droplets by employing a configuration in which geometrical conditions in a recording head are met and the meniscus of high-viscosity ink is prevented from vibrating naturally has also been proposed (for example, see JP-A-2005-119296).
Incidentally, when the high-viscosity liquids are ejected using a liquid ejecting apparatus, it is more difficult for the liquid to move within the nozzle and the liquid ejection is prone to drops in efficiency, as compared to the ejection of low-viscosity liquids. Furthermore, when liquid droplets are actually ejected, there is a tendency for the portion of the ejected droplet at the rear of the flight direction to extend as a tail (this phenomenon will be referred to as “trailing tails” hereinafter). If trailing tails occur, there is the possibility that the impact shape (dot shape) on the impact target will be disrupted. In other words, a circle, an ellipse, or the like of a target size is desirable as the impact shape from the standpoint of image quality or device capabilities; however, there has been a problem in that if the liquid droplet impacts in a state in which the tail portion is protruding from the main impacted portion of the droplet, the impact shape will be a distorted shape, rather than a circle or an ellipse. Meanwhile, in the case where all or part of the tail separates from the primary droplet as mist (satellite droplets), there is the possibility that that mist will impact upon the impact target in a different position than the primary droplet. Such disturbance in the impact shape is a cause of image quality degradation when, for example, an image is recorded onto recording paper by a printer.